Newton's second law ties the rate of change of momentum to the force applied, and a 5 kg body at 2 m/s² needs a net force of 10 N, so this Class 11 sheet opens with the law and its F = ma check. Momentum change and inertial frames sit in the answers.
Key Takeaways
Rate of change of momentum is proportional to force applied (Q1).
A 5 kg body accelerating at 2 m/s² needs a 10 N net force (Q2).
Q4 records change in momentum among the answers.
Section A: Multiple Choice Questions (1 Mark Each)
Choose the correct option for each question.
1.According to Newton's second law, the rate of change of momentum of a body is directly proportional to the:
(a) force applied(b) velocity of the body(c) displacement of the body(d) mass of the body
2.A body of mass 5 kg accelerates at 2 m/s². The net force acting on it is:
(a) 5 N(b) 10 N(c) 2 N(d) 25 N
3.Friction always acts:
(a) in the direction of motion(b) perpendicular to the motion(c) in the direction of the applied force(d) opposite to the direction of relative motion
4.Impulse of a force is equal to the:
(a) change in momentum(b) change in force(c) change in velocity(d) change in mass
5.To just start a block moving on a horizontal surface, a force F is required when the normal reaction is N. The coefficient of static friction is:
(a) F/N(b) N/F(c) F × N(d) F − N
6.For a body moving in a uniform circular motion, the centripetal force acts:
(a) away from the centre(b) towards the centre(c) along the tangent(d) it is zero
Section B: Short Answer Type Questions (2 Marks Each)
Show all steps clearly.
7.State Newton's first law of motion and explain the concept of inertia.
8.State Newton's third law of motion with one everyday example.
9.Define impulse and write its SI unit.
10.Distinguish between static friction and kinetic friction. Which is generally larger for the same pair of surfaces?
11.Define centripetal acceleration and write its expression for uniform circular motion.
12.Why is the outer edge of a road raised at curves? Write the expression for the optimum speed on a banked road.
13.State Newton's second law and derive the relation F = ma from it.
14.Write the relation between the momentum p and kinetic energy K of a body.
Section C: Numericals & Word Problems (3 Marks Each)
Apply the concepts to solve the problems. Show all working.
15.A car of mass 1000 kg accelerates uniformly from rest to 20 m/s in 10 s. Using F = ma and a = (v − u)/t, find the average force acting on the car.
16.A constant force of 10 N acts on a body of mass 2 kg for 5 s. Using impulse = F × t = change in momentum, find the impulse and the change in velocity of the body.
17.A block of mass 10 kg rests on a horizontal surface where the coefficient of static friction is 0.4. Taking g = 10 m/s² and using f = μN, find the minimum horizontal force needed to just start the block moving.
18.A car of mass 1500 kg takes a circular turn of radius 50 m at a speed of 20 m/s. Using F = mv²/r, find the centripetal force required.
19.A body of mass 2 kg moving at 5 m/s rebounds with a velocity of 3 m/s in the opposite direction. Using impulse = m(v − u), find the magnitude of the impulse.
20.A stone of mass 0.5 kg is whirled in a vertical circle at the end of a string of length 1 m. At the top of the circle its speed is 4 m/s. Using T + mg = mv²/r and taking g = 10 m/s², find the tension in the string.
Answer Key
1. a) force applied
2. b) 10 N
3. d) opposite to the direction of relative motion
4. a) change in momentum
5. a) F/N
6. b) towards the centre
7. Refer to solution guide.
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20. Refer to solution guide.
End of Worksheet
People Also Ask
What is the rate of change of momentum proportional to?
The force applied, option (a) in this worksheet (Q1).
What net force accelerates a 5 kg body at 2 m/s²?
10 N, option (b) in this worksheet (Q2).
What does impulse equal?
Change in momentum, option (a) in this worksheet (Q4).
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